You can verify that both TeXmaker and TeXstudio produce the document structure outline by direct analysis of the .tex source code. No analysis of the .aux file is performed (which would give better results in the sense that the outline would resemble the actual TOC, but would require a TeX run and thus risks lagging behind the document source).
At least for TeXstudio the document structure can be influenced via the .cwl file used for autocompletion. Commands marked with #L0 to #L5 will appear in the outline (see http://texstudio.sourceforge.net/manual/current/usermanual_en.html#CWLDESCRIPTION). So if you marked up \printbibliography as #L1 it should appear as \chapter in the outline. Trial and error, however, suggests that this only works properly if the command takes a mandatory argument that contains the title. This is not the case for \printbibliography. In my tests the following .cwl worked
\myprintbibliography{title}#L1
\myprintbibliography[key=value, ...]{title}#L1
with this definition of \myprintbibliography
\newcommand*{\myprintbibliography}[2][]{%
\printbibliography[#1, title=#2]
}
But of course that isn't really a good option.
TeXmaker on the other hand has a slightly less extensible auto-complete feature (see for example How can I make texmaker autocomplete commands that it doesn't already autocomplete?) and does not appear to allow for customisations of the document structure.
In any case I suggest you contact the developers of your editor about this. Note that it would require extensive analysis of the document code to accurately determine the level and title of the bibliography in all cases. The default heading level of \printbibliography and the title change between article-like classes and report/book. The heading and title options can influence this as well. Lastly, a user can always redefine the default bibheadings, changing the heading level and more. Similarly for BibTeX-based \bibliography. Usually the document class defines the level of the heading and the title, but this can all be changed by included packages (and sometimes their options).
There is nothing the LaTeX side of things can do about this.
biblatexor any other package can do something about. – moewe Jun 13 '19 at 16:25